Means for preventing corona losses.



G. FACCIOLI.

MEANS FOR PREVENTING CORONA LOSSES. APPLICATION FILED MAY 11, 1912.

1 1 90, 1 35 Patented July 4, 1916.

Fig. 2.

Witnesses: Inventor: /z Giuseppe Faccioli,

' His .7Tttorneg.

farther and.

UNITED STATES PATENT OFFICE.

GIUSEPPE'FACCIOLI, 0F PITT SFIELD, MASSACHUSETTS, ASSIGNOR TO GENERALELECTRIC COMPANY, A. 3ORPORATION- OF NEW YORK.

I FOR PREVENTING CORONA LOSSES.

Original application filed April 27, 1911, Serial No. 623,630. Dividedand Serial No. 696,552.

To all whom it may concern:

Be it known that I, GIUsEPPE FACCIOLI, a subject of the King of Italy,residing at Pittsfield, county of Berkshire, State of Massachusetts,have invented certain new and useful Improvements in Means forPreventing Corona Losses, of which the following is a specification.

This application is a division plication filed April 27th,, 1911,623,630. I

My invention relates to the prevention and to the reduction of thecorona losses which appear when high potential is' appliedto electricalconductors and electrical apparatus of the type heretofore commonlyused. The corona or luminous discharge from the conductor or apparatusinto the air represents considerable loss of energy and also facilitatesshort circuits and dischargesfrom the conductor to ground.

Ordinary insulating materials break down and become conducting ifsubjected to high enough voltageand if the voltage between -a wire ofthe transmission line, for example, and either the other wire or theground is gradually increased, it ultimately passes beyond the pointwhere the air is insulating, whereupon corona is produced because theair surrounding the Wire breaks down and becomes a conductor. Theconducting air envelop surrounding the wire is in turn surrounded bynon-conducting air, but as the voltage gradually increases stillfurther, the area of broken down or conducting air surrounding the wirespreads farther from the wire, thereby enlarging the luminous zone ofcorona until of my ap- Serial No.

' this area spreads to such an extent that it the wire breaks down andluminosity begins merges with the corresponding area surrounding theother wire, or else touches a ground, and current can fiow from the wirethrough the conducting air to the other wire or to ground.

For any given size of Wire there is a certain critical voltage at whichthe air around This is the critical voltage at which corona appears. Athigher voltages the corona extends to greater distances from the wireand a greater volume of air becomes luminous. Up to the critical voltagethere is practically no loss from corona, but beyond the criticalvoltage the corona losses increase Specification of Letters Patent.

Patented J uly 4, 1916.

this application filed May 11, 1912.

very rapidly. A simple method of determining the critical voltage, orthe voltage where corona forms, is to raise the voltage gradually inperfect darkness until the wire begins to be luminous. It is found thatthe point between where the Wire is perfectly dark and where it isluminescent can be meatsured within the fraction of one per cen Withinthe limits of the sizes of wire ordinarily used in the construction ofelectrical apparatus and of transmission lines, the critical voltage ofa small wire is lower than that of a large wire. 'In some kinds ofapparatus, and particularly on a long transmission line, the coronalosses on very high voltage conductors will be prohibitive unless theconductors are made much larger than would be necessary if their sizewere determined merely by the mechanical strength required or by thecross section of metal necessary to carry the current most economically.

The phenomenon of corona may also be considered with reference to theelectrostatic field which surrounds a Wire carrying current. Vhencurrent is flowing the wire is surrounded by a magneticfield which maybe represented by lines of force in the form of circles around the wire,while at the same time the voltage produces in the surrounding air acondition of electrostatic stress which may be represented by lines ofelectrostatic force issuing from the wire and perpendicular to itssurface. The density of the lines of electrostatic force will beproportional to the voltage gradient or the voltage per centimeter,length of the electrostatic circuit, and if'the number of lines ofelectrostatic force per inch in air rises beyond a certain criticalvalue the air ceases to be aninsulator and becomes conductive, whereuponcorona appears. At the critical voltage the density of the lines ofelectrostatic stress reaches the critical value which is necessary tocause the air to break down.

The object of my invention is to prevent allvor practically all of thecorona losses which occur on the conductors and in the electricalapparatus ordinarily used when which much higher potentials may beapplied without producing corona than can be applied to conductors ofthe same current carrying capacity and constructed in the ordinarymanner; to provide a construction by means of which conductors adjacentto ground, such as conductors passing through entrance bushings andwalls, or passing near the metal towers of a transmission line, may

be subjected to much higher potentials with out danger of a breakdown toground than is the case with conductors constructed in accordance withthe practice heretofore followed; to provide means to eliminate thecorona losses which occur at the point where a conductor passes from oneinsulating medium into another; and in general to provide conductors andapparatus of which the critical voltage is much higher than the criticalvoltage of the conductors and apparatus generally used heretofore.

My invention will best be understood in connection with the accompanyingdraw a form of conductor having a critical voltage much higher than thecritical voltage of a wire such as ordinarily used. In this particularform of my invention a plurality of longitudinal wires or conductingelements 3 are connected at intervals to transverse conductors. 4 sothat the entire conductor is in the form of a coarse network. I havefound that if the wire or conducting element, such as the conductingelement 8., is joined to a transverse wire or conductor, such as the'cross piece 4, both the conducting element 3 and the transverseconductor 4 are shielded or protected for a considerable distance fromthe junction, so that when the voltage applied to the conducting element3 is gradually raised until the appearance of corona, those portions ofthe conducting element or wire and the transverse conductor which arenearest the junction are the last portions to become luminous. In theform of conductor shown in Fig. 1 the transverse wires or conductors 4are so spaced that the protected zones around each junction merge oroverlap to a limited extent so that the critical voltage of theconductor as a whole is much higher'than it would be if the transverseconductors or wires 4 were not present and very considerably higher thanthe critical voltage of a solid cylindrical conductor having the samecross section as the longitudinal conducting element 3.

' Under some conditions in which the potential on the form of conductorshown in Fig. 1 is maintained at a point very close to the criticalvoltage of the conductor, it may be desirable to make the conductor insuch a form that there will be no sharp bends or points at which theelectrostatic stress may concentrate sufliciently to break down the air.In such cases the conductor will preferably be made in the form of acylinder, as shown in Fig. 2, in which the coarse network is shaped intosubstantially a cylindrical or tubular form to render the distributionof the electrostatic stress due to potential on the conductor as uniformas possible throughout the air surrounding the conductor.

The various forms of my invention above shown are merely for purposes ofillustration and the principles disclosed therein may be used in manyother ways and for many other kinds of conductors than thoseillustrated. I therefore do not wish to be restricted to the precisearrangements disclosed, but aim in the appended claims to cover allmodifications within the spirit and scope of my invention.

WV hat I claim as new and desire to secure by Letters Patent of theUnited States, is

l. A conductor for high tension currents comprising a plurality ofinsulated current carrying elements connected in multipl'ean'd aplurality of transverse conductive v mechanical supports spaced awayfrom one another and along said elements atlinterva'lsin firm engagementtherewith to electrically connect said elements and mechanically supportand space them.

2. An insulated high potential conductor having smooth edgedlongitudinal conducting elements and transverse mechanical su ports ofmetal in firm engagement with said longitudinal portions and forming anangle therewith, said supports being spaced away from one another alongsaid conductor at intervals which cause said supports to mechanicallyhold said longitudinal portions in proper relation and renders thecritical voltage of the conductor higher than that of a.

cylindrical conductor having a cross section equal to the combined crosssections of said longitudinal portions.

3. A high voltage conductor comprising a. plurality of insulatedlongitudinal conducting elements arranged side by side and connected inmultiple and a plurality of transverse conductive mechanical supports inelectrical engagement with said longitudinal elements and spaced awayfrom one another and along said longitudinal elements at intervals tomechanically hold said elements in definite relation and to render thecritical voltage of said conductor higher than the critical voltage ofthe wire having a cross section equivalent to the combined crosssections of said longitudinal elements.

4. A conductor for high tension currents comprising a plurality ofinsulated longitudinal current carrying elements mounted side by sideand connected in multiple and a plurality of transverse conductivemechanical supports, each looped around the said longitudinal elementsto mechanically maintain said elements properly spaced and to makemetallic connection therewith.

5. A high voltage conductor comprising a plurality of insulatedlongitudinal current carrying elements connected in multiple and mountedabout a common axis to form a longitudinal conductor, and transverseconductive mechanical supports spaced away from one another andencircling said longitudinal elements and in metallic contact therewith,said members being spaced along said elements to render the criticalvoltage of said conductor higher than the critical voltage of the wirehaving a cross section equal to the size of the cross sections of saidlongitudinal elements.

6. A. conductor comprising a plurality of insulated current carryingelements connected in multiple and arranged about a common axis to forma tubular conductor, and conductive mechanical supports in the form ofloops looped around each of said longitudinal elements to make metalliccontact therewith, said rigid loops being spaced along said elements tohold said elements in position and to afi'ect the critical voltage ofthe current carrying elements.

In witness whereof, I have hereunto set my hand this 9th day of May,1912.

GIUSEPPE FACCIOLI.

Witnesses:

G. R. BLAKELY, M. TAYLOR DANNRENTHER.

